Reciprocating floor slat conveyor systems are well-known. These systems are often built into the floors of truck trailers that haul materials in bulk.
The typical reciprocating floor slat conveyor system consists of multiple, bearing mounted, parallel floor slats that are driven back-and-forth in a reciprocating action. The action or motion of the floor slats are typically driven in “stages” as follows: First, in the case of truck trailers, all of the slats are moved in one direction, at the same time. This stage moves the load on the floor a short distance toward the exit end of the trailer. Then, a lesser number of slats are retracted, or returned, in the opposite direction (typically, in stages of one-third of the slats at a time). Because of the fewer number of moving slats involved in the return stage, the greater total friction between the load and the larger number of nonmoving slats allows the moving slats in the return stage to slide underneath the load, without moving the load backward.
Returning one-third of the slats at a time, in three separate return stages, brings all of the slats to the original start position, with the load staying in place during the return stages. Once all of the slats return, then the sequence repeats itself, with all of the slats moving, once again, toward the exit end of the trailer. This, in turn, also moves the load another short distance toward and out from the exit end of the trailer. Repetitive cycling of the slats in stages in the manner just described causes the load to be inched out from the trailer.
There is a specialized market for conveyors like the above. These systems have become a substitute for and have replaced hydraulic dump lifts for certain kinds of applications. From the standpoint of historical development, these kinds of conveyors may have been initially developed to haul bulk silage for cattle feed and similar kinds of bulk materials. Since then, they have been adapted for many other uses, such as the garbage hauling markets; and certain kinds of specialized designs have been developed that allow trucks with these conveyors to haul rock, gravel, or asphalt.
As a consequence of different market needs, many different kinds of floor slat configurations have been designed over the years to adapt reciprocating floor slat conveyors to different hauling scenarios. The floor slats themselves are usually made from aluminum, for reasons relating to weight (i.e., light weight systems are desirable for truck trailers), and due to manufacturing and installation considerations. Long lengths are required for a typical floor slat (generally corresponding to the length of a trailer). Aluminum slats can be mass produced by extrusion.
For reasons relating to the abrasive wear caused by certain kinds of loads, there has been a need to develop a successful steel floor slat system in lieu of aluminum slats. Steel slats have been used in the past in combination with aluminum slat parts. For example, spaced-apart, inverted “V”-shaped reciprocating slats have been made of steel and used in combination with spaced-apart “fixed” slats made of aluminum. This system has been used to haul certain kinds of heavy bulk material that create loading impacts and abrasive wear on the moving slat—large rock would be an example. In this design, the “moving” steel slats provide better wear characteristics for the load-carrying surfaces. They are spaced from each other a certain distance and ride on bearings that are supported by the underlying “fixed” aluminum slats. This design, as a whole, creates peaks and valleys from one side of the trailer to the other side, which is a function of the “V” shape.
The use of steel in the “V” configuration is a better design relative to all-aluminum systems for certain kinds of specialized hauling applications. However, although the design works well for certain hauling applications, it does not provide a conveyor floor surface that can be driven on with a forklift. This is a drawback that limits the use of trailers that have this type of floor configuration. In other words, the trailer tends to be used “one way” and is empty on the return.
Truck haulers would like a “steel” floor slat system that can handle the specialized loads carried by a “V”-shaped steel slat system, but one that also provides a flat conveyor floor surface, from side-to-side, so that a forklift can be driven onto the trailer's floor when empty. This would allow the same trailer to be used to haul heavy bulk materials in one direction, but after unloading, the trailer can be loaded by a forklift in a conventional way with palletized loads, if desired. This is more utilitarian and allows the trailer to be used to generate revenue on the back-haul, rather than come back empty.
For the above reason, and others discussed below, there has been a long felt need for an “all steel” reciprocating floor system that can provide multiple uses. Because of the difficulty of manufacturing a suitable steel slat system, as of yet, the reciprocating floor slat industry has been unable to create a commercially viable “all-steel” floor slat design that can provide a flat, driveable surface inside the trailer.
The foregoing and other features will be better understood upon review of the drawings and description that follows.